Rails模型has_many有多个foreign_keys

Question

相对较新的rails并尝试使用具有name,gender,father_id和mother_id(2个父项)的单个Person模型来建模一个非常简单的族"树".下面基本上是我想要做的,但显然我不能重复:has_many中的孩子(第一个被覆盖).

class Person < ActiveRecord::Base
  belongs_to :father, :class_name => 'Person'
  belongs_to :mother, :class_name => 'Person'
  has_many :children, :class_name => 'Person', :foreign_key => 'mother_id'
  has_many :children, :class_name => 'Person', :foreign_key => 'father_id'
end

是否有一种简单的方法可以将has_many与2个外键一起使用,或者根据对象的性别更改外键？或者还有其他/更好的方式吗？

谢谢!

Answer 1

在IRC上找到一个似乎有效的简单答案(感谢雷达):

class Person < ActiveRecord::Base
  belongs_to :father, :class_name => 'Person'
  belongs_to :mother, :class_name => 'Person'
  has_many :children_of_father, :class_name => 'Person', :foreign_key => 'father_id'
  has_many :children_of_mother, :class_name => 'Person', :foreign_key => 'mother_id'
  def children
     children_of_mother + children_of_father
  end
end

Answer 2

为了改进Kenzie的答案,您可以通过定义以下内容来实现ActiveRecord Relation Person#children:

def children
   children_of_mother.merge(children_of_father)
end

有关详细信息,请参阅此答案

Answer 3

在Person模型上使用named_scopes执行以下操作:

class Person < ActiveRecord::Base

    def children
      Person.with_parent(id)
    end

    named_scope :with_parent, lambda{ |pid| 

       { :conditions=>["father_id = ? or mother_id=?", pid, pid]}
    }
 end

Answer 4

我相信你可以使用:has_one实现你想要的关系.

class Person < ActiveRecord::Base
  has_one :father, :class_name => 'Person', :foreign_key => 'father_id'
  has_one :mother, :class_name => 'Person', :foreign_key => 'mother_id'
  has_many :children, :class_name => 'Person'
end

我会在下班后确认并编辑这个答案; )

Answer 5

我对Rails 中的关联和（多个）外键（3.2）的回答：如何在模型中描述它们，并编写迁移只适合您！

至于你的代码，这是我的修改

class Person < ActiveRecord::Base
  belongs_to :father, :class_name => 'Person'
  belongs_to :mother, :class_name => 'Person'
  has_many :children, ->(person) { unscope(where: :person_id).where("father_id = ? OR mother_id = ?", person.id, person.id) }, class_name: 'Person'
end

那么还有什么问题吗？